Hi Randy
If you are ok with post one then send me a message.
For the others where it is their first experience with my pcb group buy then do not forget to send me the proof of purchase of the Exicon double die mosfet or the mosfet driver to demonstrate you are serious about your amplifier build.
Fab
If you are ok with post one then send me a message.
For the others where it is their first experience with my pcb group buy then do not forget to send me the proof of purchase of the Exicon double die mosfet or the mosfet driver to demonstrate you are serious about your amplifier build.
Fab
The objective was to have the 3 amps to have the same following characteristics:
1) same voltage gain
2) about same feedback factor
3) about same damping factor
4) about same THD profile
Note that USSA5B can be adjusted for a little higher feedback factor thus higher damping factor and even lower THD ( if that matters). This is similar to my old USSAB amplifier. Sound wise I prefer my actual recipe...
Fab
1) same voltage gain
2) about same feedback factor
3) about same damping factor
4) about same THD profile
Note that USSA5B can be adjusted for a little higher feedback factor thus higher damping factor and even lower THD ( if that matters). This is similar to my old USSAB amplifier. Sound wise I prefer my actual recipe...
Fab
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USSA5.1 had only one channel assembled due to lack of pcbs. Meanie and a Vunce who had both built the original USSA5 are volunteers to also build the USSA5.1 which is very Diy spirit 
Recently I have found 2 Proto pcb with lower quality I did not remember I had which allowed me to experiment with the USSA5B. The USSA5B design has been adjusted yesterday to meet the criterias I have mentioned previously but modules tested on my bench still not installed in power amp to play music. I am working on it.
But as I said, the goal of the 3 versions is to have a similar sound signature. Based on my experience with that topology I expect the USSA5.1 to sound similar to the USSA5. The USSA5B should be more different with bipolar outputs.
The goal of USSA5.1 is to have a lower cost amp with no difficult to find matched mosfet drivers. The goal of the USSA5B is to reduce further the cost. However, as a reminder, the USSA5 pcb is not meant for the bipolar output pin out thus require connection inversion.
To continue the story, the USSA5 goal was to have a bipolar input compared to higher cost jfet input of the USSA3 and also have a higher damping factor.
To complete the story, the goal of the USSA3 was to use lateral mosfet as output compared to vertical mosfet of the PASS F5. I prefer the sound of lateral mosfet over the vertical mosfet - at least up to what I have heard so far
The sound of USSA is quite different from an F5. Pass upgraded the F5 amp design to Lateral mosfet with the F7 but the latter needs positive feedback to achieve a proper damping factor. Positive feedback can be more difficult to implement but some members seem to have succeeded in the PASS forum. I believe the F7 schematics is not disclosed by PASS at this time.
Fab
Recently I have found 2 Proto pcb with lower quality I did not remember I had which allowed me to experiment with the USSA5B. The USSA5B design has been adjusted yesterday to meet the criterias I have mentioned previously but modules tested on my bench still not installed in power amp to play music. I am working on it.
But as I said, the goal of the 3 versions is to have a similar sound signature. Based on my experience with that topology I expect the USSA5.1 to sound similar to the USSA5. The USSA5B should be more different with bipolar outputs.
The goal of USSA5.1 is to have a lower cost amp with no difficult to find matched mosfet drivers. The goal of the USSA5B is to reduce further the cost. However, as a reminder, the USSA5 pcb is not meant for the bipolar output pin out thus require connection inversion.
To continue the story, the USSA5 goal was to have a bipolar input compared to higher cost jfet input of the USSA3 and also have a higher damping factor.
To complete the story, the goal of the USSA3 was to use lateral mosfet as output compared to vertical mosfet of the PASS F5. I prefer the sound of lateral mosfet over the vertical mosfet - at least up to what I have heard so far
The sound of USSA is quite different from an F5. Pass upgraded the F5 amp design to Lateral mosfet with the F7 but the latter needs positive feedback to achieve a proper damping factor. Positive feedback can be more difficult to implement but some members seem to have succeeded in the PASS forum. I believe the F7 schematics is not disclosed by PASS at this time.
Fab
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Hi Fab,
Payment sent and PM also sent.
How are you going with the full updated manual, any hints as to when you will be emailing that out to GB members who qualify for it, and will it address the 3 different schematic options you have shown above, or only the 2 with lateral outputs, thanks again?
Regards,
Gary..
Payment sent and PM also sent.
How are you going with the full updated manual, any hints as to when you will be emailing that out to GB members who qualify for it, and will it address the 3 different schematic options you have shown above, or only the 2 with lateral outputs, thanks again?
Regards,
Gary..
Hi Meanie,
I have had a quick look at Digikey, they have both in stock. Hope that helps.
By the way have you made a comparison between the SLB power supply and another maybe the one from Project16 / Prasi?
I have get my SLB PCB yesterday.
Kind regards
André
I have had a quick look at Digikey, they have both in stock. Hope that helps.
By the way have you made a comparison between the SLB power supply and another maybe the one from Project16 / Prasi?
I have get my SLB PCB yesterday.
Kind regards
André
Hi Fab, I have what may be a strange question - I have been searching for my dream amplifier.... and I am hopeful this is it. I am running 110db horn speakers, Can I bias this amplifier for 2-3 watts of Class A , I know there are other small Class-A amplifiers.... but after reading all the reviews this looks like this might be The Amplifier I've been searching for so long. -- Thank you,
Dean
Dean
Hi Gary
The manual can be used as-is for the USSA5 (I mean the full manual version) since we all know that the output mosfet are Exicon instead of Alfet.
I will update the manual for version 5.1 most probably by adding an addendum during next week. For version 5B it will be later since I prioritize to test this version in a sound system.
Fab
Hi Arthur
I suppose you have completed your USSA5 build using the pcbs you received last year. Can you show pictures or feedback on the forum.
Fab
Fab, you have good memories
I just gathered 4 pairs of driver Mosfets and 8 pairs of the output Mosfets .
As the latest 5.1 can use Darlington transistors to drive the output Mosfets, I will try assembly them in the Christmas Holiday.
Then I will compare the sound quality with my newly bought Firstwatt Sit-3
I just gathered 4 pairs of driver Mosfets and 8 pairs of the output Mosfets .
As the latest 5.1 can use Darlington transistors to drive the output Mosfets, I will try assembly them in the Christmas Holiday.
Then I will compare the sound quality with my newly bought Firstwatt Sit-3